1. Field of the Invention
This invention relates to improvements in diacetylenic phospholipids and to lipid microstructures made from these lipids. More particularly, this invention relates to diacetylenic phospholipids with at least one heteroatom spacer on the diacetylenic chains, and to lipid microstructures made from these lipids.
2. Description of the Related Art
Diacetylenic phospholipids are used in making hollow microstructures, which may be spherical (vesicles) or cylindrical (tubules). These structures are useful for microencapsulation and for controlled release of drugs, antifouling agents in marine paints, and other substances. They offer an alternative to the polymers commonly used in these applications.
Problems with the available lipid microstructures include expensive reagents, microstructure morphology with fixed dimensions, and excessive rigidity.
Microstructure morphology with fixed dimensions puts restrictions on the size of a molecule to be encapsulated with an appropriate tubule. The known diacetylenic phospholipids self-assemble into tubules that have a diameter that is specific for a given phospholipid. This creates problems in encapsulating large-diameter molecules in tubules, since the known tubules cannot adapt their growth to the diameter of the molecule they are to encapsulate.
Excessively rigid tubules are prone to breakage during their formation and processing, and thus do not provide optimal controlled release of their contents.